Miniature ecg data acquisition device

ABSTRACT

An apparatus for generating ECG recordings and a method for using the same are disclosed. The apparatus includes a handheld device having four electrodes on an outer surface thereof, the handheld device having an extended configuration and a storage configuration. The apparatus also includes a controller configured to measure signals between the electrodes to provide signals that are used to generate an ECG recording selected from the group consisting of standard lead traces and precordial traces. When the handheld device is in the extended configuration and the first and second electrodes contact a first hand of a patient such that the first and second electrodes contact different locations on the first hand, the third electrode is in contact with a location on the patient&#39;s other hand and the fourth electrode contacts a point on the patient&#39;s body that depends on the particular trace being measured.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.17/857,067, filed on Jul. 4, 2022, which is a Continuation of U.S.patent application Ser. No. 16/030,791 filed on Jul. 9, 2018, now U.S.Pat. No. 11,375,938, which is a Continuation of U.S. patent applicationSer. No. 13/710,886 filed on Dec. 11, 2012, now U.S. Pat. No.10,092,202, which is a Continuation-in-Part of U.S. patent applicationSer. No. 13/293,888 filed Nov. 10, 2011, now U.S. Pat. No. 8,412,313which is a divisional of U.S. patent application Ser. No. 12/191,923filed on Aug. 14, 2008, now U.S. Pat. No. 8,082,025. The contents of theabove applications are all incorporated by reference as if fully setforth herein in their entirety.

BACKGROUND OF THE INVENTION

ECG measurements are a standard form of cardiac measurement forassessing the condition of a patient's heart. Physicians are trained tointerpret a standard set of ECG recordings that are normally obtained byconnecting ten electrodes to the patient's body and measuring thevoltages between various electrodes and combinations of electrodes as afunction of time.

While the standard measurements are easily obtained in a medicalsetting, such measurements pose challenges when a patient is not in sucha setting, which is most of the time. A patient with heart problemswould benefit both from a clinical and psychological point of view ifthe patient could measure the standard set of recordings whensymptomatic to determine if the recordings had changed since they werelast measured. If the recordings were within the expected range, thepatient would be reassured and could go about his or her normalactivity. If the measurements were outside the expected range, thepatient could transmit them to the patient's physician, the physiciancould interpret the measurements and advise the patient accordingly or,the measurements can be transmitted automatically to a pre-definedmedical entity.

A number of systems for making measurements outside of the clinicalsetting have been proposed. These systems include some form of ECGelectrodes that are attached to the patient's body and connected to alocal processor carried by the patient. The local processor typicallyincludes a transmitter that relays the measurements from the unit wornby the patient to a physician at a remote location. The relay mechanismcan utilize a telephone line, either land or cellular, or some form ofdedicated transmitter.

The systems that duplicate the standard measurements require thatelectrodes be attached to the patient's body. To provide a full 12 leadECG recording set, electrodes are typically attached to the patient'supper and lower limbs, as well as to a number of locations on the torso.If the patient is in a setting in which the patient has only limitedmobility, such a set of attached electrodes may be acceptable; however,if the patient is fully mobile and attending to his or her normalroutine outside of a medical environment, temporary or permanentattachment of the electrodes is not usually acceptable and involves afair amount of discomfort. Furthermore, the electrodes must be removedwhen the patient bathes. Hence, some arrangement is needed in which thepatient or a caregiver places the electrodes on the patient's body atthe time an ECG is to be recorded. A system based on the use ofadhesively coated electrodes such as those utilized in normal ECGmeasurements presents problems from a logistical and cost point of view.The individual electrodes are only usable for a small number ofmeasurements before the adhesive fails. Furthermore, the repeatedplacement and removal of the electrodes can cause patient discomfort,particularly in patients having body hair in the areas to which theelectrodes must be attached. In addition, the patient is often incapableof connecting the electrodes to his or her body at all of the requiredlocations.

Hence, a system that can be utilized by the patient without the help oftrained personnel would be advantageous. One such system is discussed inthe above-identified co-pending patent application. In that system, ahandheld device with four electrodes on the surface thereof is used togenerate the 12 standard measurements. The four electrodes are used invarious combinations to contact the body at locations that the user caneasily reach. By making measurements between various electrodes andvarious contact points, a good approximation to the conventional 12standard measurements can be obtained. The device is connected to acommunication device that can be used to transmit the data to medicalpersonnel.

The size of this and other portable devices still presents challenges.The above-described device is integrated into a cellular telephone orother form of personal data device. However, it would still benefit froma significant reduction in size so that the device would be no morecumbersome to carry than a USB memory module.

SUMMARY OF THE INVENTION

The present invention includes an ECG data acquisition device and methodfor using the same. The ECG data acquisition device includes a handhelddevice having first, second, third, and fourth electrodes on an outersurface of the handheld device, the handheld device having an extendedconfiguration and a storage configuration. The ECG data acquisitiondevice also includes a controller that measures signals between theelectrodes and provides those signals to another device to generate anECG recording selected from the group consisting of standard lead tracesand precordial traces. When the handheld device is in the extendedconfiguration and the first and second electrodes contact a first handof a patient such that the first and second electrodes contact differentlocations on the first hand, the third electrode is in contact with alocation on the patient's other hand and the fourth electrode contacts apoint on the patient's body chosen from the group consisting of thepatient's lower abdomen, one of the patient's legs, and a precordialmeasurement point on the patient, the point depending on the ECGrecording. The ECG data acquisition device also includes a circuit thatgenerates a common mode cancellation signal from signals on the second,third, and fourth electrodes and couples the common mode cancellationsignal to the first electrode while the controller is measuring saidsignals.

In one aspect of the invention, the ECG data acquisition device includesa wireless communication link that transmits the measured signals to adevice that is external to the handheld device.

In another aspect of the invention, the handheld device in the storageconfiguration is too small to allow the patient to contact the first,second, third, and fourth electrodes in a manner that allows the ECGrecordings to be made.

In another aspect of the invention, the handheld device includes acompartment for storing medication, the compartment opening in responseto signals from the controller.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates the placement of electrodes and the signals that aremeasured in the “standard lead measurements” that are six of the 12recordings provided in a conventional 12 lead ECG.

FIG. 2 illustrates the measurement of the precordial traces.

FIGS. 3A-3D illustrate one embodiment of an ECG data acquisition deviceaccording to the present invention.

FIG. 4 is an end view of one embodiment of an ECG data acquisitiondevice according to the present invention when the device is gripped bythe user.

FIG. 5 is a side view of an ECG data acquisition device in a storageconfiguration after the two sections have been moved relative to oneanother for storage.

FIG. 6 illustrates the relationship between an ECG data acquisitiondevice according to one embodiment of the present invention and areceiving processor.

FIG. 7 illustrates another embodiment of an ECG data acquisition deviceaccording to the present invention.

FIGS. 8A and 8B illustrates one embodiment of a finger electrode thatcan be utilized with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The manner in which the present invention provides its advantages can bemore easily understood with reference to FIG. 1 , which illustrates theplacement of electrodes and the signals that are measured in the“standard lead measurements” that are six of the 12 recordings providedin a conventional 12 lead ECG. The standard lead measurements providerecordings as a function of time of the potentials between pairs ofelectrodes that are connected to the patient's body. For example, thefirst standard lead measurement, which is often referred to as the leadI measurement, or just Lead I, consists of the difference in potentialmeasured between the left and right wrists of the patient, as a functionof time. Similarly, the lead II measurement, or Lead II, consists of thedifference in potential, as a function of time, measured between theleft leg and the right wrist of the patient. Lead III consists of thedifference in potential, as a function of time between the left leg andthe left wrist of the patient. The remaining three leads, aVR, aVL, andaVF are differences between the potential of one limb and the averagepotential of another two limbs

Denote the potential at the right wrist or hand by Φ_(r), the potentialat the left wrist or hand by Φ_(l), and the potential the left leg byΦ_(f). The first three standard leads or traces are given by

I=Φ _(l)−Φ_(r),

II=Φ _(f)−Φ_(r), and

III=Φ _(f)−Φ₁ =II-I  (1)

As noted above, these signals are each functions of time. In thefollowing discussion, the Lead I signal as a function of time will bereferred to as the hand signal. The Lead II signal as a function of timewill be referred to as the leg signal.

Three additional traces are generated by utilizing weighted sums anddifferences of the Lead I and II signals, namely

aVR=Φ _(r)−(Φ_(l)+Φ_(f))/2=−(I+II)/2,

aVL=Φ _(l)−(Φ_(r)+Φ_(f))/2=I−II/2, and

aVF=Φ _(f)−(Φ_(r)+Φ_(l))/2=II−I/2.  (2)

The remaining six traces of the conventional 12 lead ECG are theprecordial traces (V₁-V₆) Refer now to FIG. 2 , which illustrates themeasurement of the precordial traces. In the conventional precordialmeasurements, each trace is generated by forming the average of thepotentials at the right and left wrists and the left leg (this averagedpotential is known as Wilson's Central-Terminal Φ_(CT)) and thenmeasuring the difference between a potential, Φ_(i), detected by anelectrode at a corresponding point on the patient's chest and Φ_(CT). Adifferent predetermined point on the chest is used for each of the sixtraces:

V _(i)=Φ_(i)−(Φ₁+Φ_(f)+Φ_(r))/3=Φ_(i)−Φ_(CT),  (3)

where Vi (i=1 . . . 6) are the precordial leads. The average signal fromthe hands and leg is often referred to as the “C-terminal”. It should benoted that a C-terminal signal can be generated from other locations onthe three extremities in question. For example, the potentialscorresponding to the leg can be measured at the foot, ankle, or upperthigh or lower abdomen. Similarly, the potentials corresponding to the“hands” can be measured any place between one of the fingers and theshoulder.

It should be noted that the traces are always measured as a differencein potential between two electrodes placed on the correspondinglocations on the patient's body by utilizing differential amplifiers toform the differences of the signals in question. Ideally, this procedureeliminates the effects of common mode signals that are picked up by thepatient's body such as the 50 or 60 cycle AC signals that are present inmost indoor environments. Unfortunately, the magnitudes of the commonmode signals are much greater than that of the heart signals that arethe subject of the measurements in question, and the availabledifferential amplifiers have a common mode rejection figure that isinsufficient to eliminate all of the common mode noise in question.

To reduce the common noise, a signal that is a good approximation to asignal that would cancel the common mode signal in the patient's body isgenerated and then injected into the right ankle in conventional ECGmeasurement devices. This signal will be referred to as the common modecancellation signal in the following discussion. The common modecancellation signal must be injected at a location that will notinterfere with the measurement of the signals from the ECG electrodes.The common mode cancellation signal reduces the common mode signal inthe patient's body by canceling the common mode signal that is picked upfrom the patient's body, and hence, reduces the problems associated withthe large difference between the common mode noise and the signals ofinterest, since the signals of interest no longer have a large commonmode signal as part of each signal.

In the prior art, an electrode attached to the right ankle is used asthe injection point for the common mode cancellation signal. This doesnot present a significant problem with respect to the signals detectedby the other electrodes, since the right ankle is far from the locationof the other electrodes, and hence, any localized signal variations aredissipated by the time the cancellation signal reaches the portions ofthe body near the electrodes of interest. Since the C-terminal signal isan average of the potentials at widely separated points on the patient'sbody, the inverse of the C-terminal signal is often utilized as thecommon mode cancellation signal. That is, the inverse of the C-terminalsignal is injected into the right ankle to reduce the common mode noise.

The present invention is based on the observation that a goodapproximation to the conventional 12 lead ECG measurements can beobtained by using a handheld probe that has four electrodes on the outersurface of the probe. Refer now to FIGS. 3A-3D, which illustrate oneembodiment of an ECG data acquisition device according to the presentinvention. ECG data acquisition device 20 has an extended configurationand a storage configuration. FIG. 3A is a top view of ECG dataacquisition device 20 in the extended configuration; FIG. 3B is a sideview of ECG data acquisition device 20 in the extended configuration,and FIG. 3C is a bottom view of ECG data acquisition device 20 in theextended configuration. FIG. 3D is a side view of ECG data acquisitiondevice 20 in the storage configuration, which in the case of ECG dataacquisition device 20 is a folded configuration. When being used tomeasure ECG recordings, ECG data acquisition device 20 is operated inthe extended configuration. For storage, ECG data acquisition device 20is folded. In one embodiment, the ECG data acquisition device measuresless than 7 cm in the folded configuration.

It should be noted that providing a very small object that is carried bythe user when not being used is important. If the object is large, theuser will not carry it with the user. A device that is the size of amemory stick when in the storage configuration can easily beaccommodated on a key chain or the like. Hence, the user is notinconvenienced by having the device with the user at all times. In oneaspect of the invention, the ECG data acquisition device includes one ormore buttons such as button 44 that are used for providing user inputsinto the ECG data acquisition device. These buttons can be used by theuser to signal the ECG data acquisition device that the user wishes toperform a specific measurement such as one particular ECG recording.

In addition, these buttons can be used to input data that is not relatedto the ECG measurements. As noted above, providing a device that issmall enough to encourage the user to carry the device with the user atall times is an important consideration. To the extent that the ECG dataacquisition device can provide some other function that the user wouldlike, the other function increases the probability that the user willhave the ECG data acquisition device with the user when a suspectedcardiac event is occurring. In one aspect of the invention, the ECG dataacquisition device also serves the function of an electronic key. Forexample, the user could input a code to the ECG data acquisition devicethrough the buttons that causes the ECG data acquisition device toutilize its wireless link to perform some function such as an electronickey for an automobile or a garage door opener. Hence, the ECG dataacquisition device can also replace an electronic key that the userwould normally carry thereby increasing the probability that the userwould have the ECG data acquisition device when needed. In this regard,it should also be noted that the ECG pattern of one Lead I trace isknown to vary from person to person, and hence, this pattern can be usedas a biometric key that enables the key function in question.

While the keypad function described above is implemented using separatekeys, it should be noted that the function could be implemented using atouch-enabled display as display 40. The preferred method for inputtingthe required data depends on the available power. The keypad requiresless power. In addition, electronic car keys typically have a fewbuttons to provide the functions on the key, and hence, the user isfamiliar with the button implementation.

Referring to FIGS. 3A-3C, ECG data acquisition device 20 includes fourelectrodes shown at 21-24, respectively. A 12 trace ECG diagram isobtained using ECG data acquisition device 20 by holding the ECG dataacquisition device with both hands and pressing electrode 24 against theappropriate place on the patient's body. Refer now to FIG. 4 , which isan end view of ECG data acquisition device 20. In one embodiment,electrodes 21 and 22 are held in the right hand 31 with the thumb 32 onelectrode 21 and the right index finger 34 on electrode 22. The leftindex finger 33 or any part of the left palm is held on electrode 23. Itshould be noted that electrode 22 can be touched with other fingers ofthe right hand besides the index finger. Electrode 21 can also betouched with other fingers or part of the right hand. Referring again toFIGS. 3A-3C, for the standard lead measurements, electrode 24 is placedagainst any point of the left leg or the lower abdomen. For theprecordial measurements, electrode 24 is placed sequentially at each ofthe precordial positions on the patient's chest.

As noted above, the four conventional electrodes are placed on the leftand right wrists and the left and right ankles. In the presentinvention, these measurements are provided by using the potential at theright index finger, i.e., electrode 22, in place of the potential at theright wrist, the potential at the right thumb, i.e., electrode 21 inplace of the potential at the right ankle, the potential at the leftindex finger, i.e., electrode 23, in place of the potential at the leftwrist, and the potential at the left leg, i.e., electrode 24 in place ofthe potential at the left ankle.

The common mode cancellation signal is injected into the right thumbthrough electrode 21 in this embodiment of the present invention. It hasbeen observed that using the thumb for the common mode cancellationsignal injection site provides the desired cancellation of the commonmode noise without significantly interfering with the measurements ofthe ECG recordings even though the signal from the right index finger isused to generate the ECG recordings. It should be noted that usinganother finger on right hand for the injection of the signal has beenfound to provide more interference with the recordings than the use ofthe thumb. Accordingly, the thumb is preferred. In addition, using thethumb and index finger to grip the electrodes provides a morecomfortable operating position then using another location on the righthand.

The above-described embodiments are optimized for a right-handed user.However, the device can equally be utilized by a left-handed user. Whenused by a left-handed user, thumb and index finger of the left handcontact electrodes 21 and 22 and the user touches electrode 23 with afinger or thumb of his or her right hand. It should also be noted thatthe common mode rejection signal can be injected into the index fingerthat is contacting electrode 22 and the measurements made through thethumb that contacts electrode 21. The specific arrangement can be set inthe software that is downloaded to the ECG data acquisition device andcustomized to the particular user.

In the present invention, the common mode cancellation signal is derivedfrom the sum of the signals from electrodes 22, 23 and 24 denoted by Φ₂₂Φ₂₃ and Φ₂₄ respectively. During the standard lead measurements, thecommon mode cancellation signal is analogous to the conventional commonmode cancellation signal, as it corresponds to the C-terminal signal.During the precordial measurements, the chest signal is recorded onelectrode 24. However, it has been found experimentally, that theresultant common mode cancellation signal is still sufficient to providethe necessary level of common mode signal reduction.

ECG data acquisition device 20 is constructed from sections 27 and 28that are hingedly connected by hinge 26. However, other arrangements inwhich the two sections move apart by sliding with respect to one anotherfor use during measurements could be utilized. Such an arrangement isshown in FIG. 5 , which is a side view of an ECG data acquisition device50 in a storage configuration after the two sections shown at 57 and 58have been moved relative to one another for storage.

In one aspect of the invention, the extended configuration providesthree electrodes that are spaced apart sufficiently to allow theelectrodes to be contacted with a finger of one hand and two fingers ofthe other hand and still provide a fourth electrode that can be placedat various locations on the patient's body while the patient is holdingthe device with the fingers contacting the electrodes. While makingmeasurements, it is important that the user's hands from the wrist up tothe armpits do not touch any part of the bare torso or other bare bodypart, as such contact would alter the effective electrical path from theheart to the wrists. If any other part, such as the barehanded forearmtouches the bare torso, or bare leg, the ECG readings could be alteredand would not represent the true signals derived from the heart.

In one aspect of the invention, the distance between electrode 24 andthe group electrodes 21, 22 and 23 in the extended configuration is setsuch that the user is forced to lift the user's elbows to the side, thuspositioning the user's arms away from the user torso or leg. The lengthof the extension in the extended configuration is used to maintain therequired arm placement. In another aspect of the invention, the presentinvention is provided with extensions of different lengths toaccommodate variations in body types and sizes between various users.The extensions can telescopic into one another such that the extensionsdo not significantly increase the size of the device when the device isplaced in the storage configuration even with the longest extension. Thetelescopic extension increases the distance between electrodes 24 andthe group of electrodes 21, 22 and 23.

In the storage configuration, the device is more compact than in theextended configuration. That is, the user could not hold the device withthe finger so contacting the electrodes and the fourth electrode beingavailable for contacting the other points on the patient's body. In oneaspect of the invention, the device has a maximum dimension of less than7 cm in the storage configuration and opens up to a device that has amaximum dimension greater than 12 cm. The minimum sized device in themeasurement configuration must be large enough to accommodate twofingers gripping electrodes 21 and 22 and be long enough to placeelectrode 24 against the various locations at which recordings are to bemade without the arms or hands coming in contact with the torso of thepatient.

Refer now to FIG. 7 , which illustrates another embodiment of an ECGdata acquisition device according to the present invention. ECG dataacquisition device 70 is configured to resemble a pen and sized to fitin the user's pocket in a manner analogous to the manner in which a penis clipped into a pocket. In this case, clip 74 provides the clipfunction. ECG data acquisition device 70 includes a first section 71that includes electrodes 21-23 and a bottom section 72 that includeselectrode 24. Section 72 can move into section 71 to provide a morecompact device in the storage configuration. In some cases, the movementof section 72 into section 71 may not be needed. For example, a devicethat has a length of a conventional pen may function adequately forindividuals with a range of body types. For individuals that areoverweight a longer device may be needed, and hence, the ability toextend the length is desirable.

ECG data acquisition device 70 also includes one or more LEDs such asLED 76 that are utilized to signal the user as to the next operation tobe performed when making measurements. Clip 74 can also act as a releasefor moving or locking sections 71 and 72 with respect to one another. Itshould also be noted that embodiments in which clip 74 provides thefunction of one of the hand electrodes could also be constructed.

It should be noted that for some users, the length of the pen in thestorage configuration may be sufficient to provide the spacing functiondiscussed above during measurements. Hence, ECG data acquisition device70 is configured to be operative for making measurements in both thestorage configuration and the extended configuration. The two sectionsof ECG data acquisition device 70 can include a spring mechanism thatcauses the sections to move to the extended configuration when clip 74is pushed. While the conversation between the storage and extendedconfiguration utilizes clip 74 in the embodiment shown in FIG. 7 , otherrelease mechanisms could be utilized.

The size of the device in the extended configuration can beadvantageously increased for making measurements on persons with limitedflexibility such as elderly persons. In such cases, a device that islarger and more easily grasped may be preferred.

In one aspect of the invention, the ECG data acquisition device includesthe electronics for providing the signals corresponding to the I, II,and an approximation to V_(i). The device also generates the signalequal to the inverse of the potentials on electrodes 22-24 and couplesthat signal to electrode 21. The approximation to V_(i) is given by

V _(i)=Φ_(i)−(Φ_(l)+Φ_(r))/2=Φ_(i)−Φ′_(CT)  (4)

The common mode cancellation signal is

V ₂₁=−(Φ₂₂+Φ₂₃+Φ₂₄)/3  (5)

In one aspect of the invention, the ECG data acquisition devicetransmits signal values for I, II, and V_(i) as a function of time via awireless link to a receiving processor. Refer now to FIG. 6 , whichillustrates the relationship between an ECG data acquisition deviceaccording to one embodiment of the present invention and a receivingprocessor. A receiving processor is defined to be any computationaldevice with sufficient computational capacity to compute the 12conventional ECG recordings from these signals. The receiving processor61 could be a portable device that the user also carries with the useror a fixed device within range of the wireless link. For example, thesesignals can be transmitted to a receiving processor 61 comprising smartphone, personal data assistant (PDA), tablet computer, or laptoppersonal computer via Bluetooth, WiFi, or other wireless communicationlink. If the user is within range of a PC or other non-portablecomputer, that computer could also be used as the receiving processor.The computational capacity of the receiving processor is used toconstruct the ECG recordings. Since the precordial measurements areprovided one at a time, the receiving processor 61 also provides signalsthat are displayed on the ECG data acquisition device 62 to signal theuser as to the next contact point for the fourth electrode. Refer againto FIG. 3A. In one aspect of the invention ECG data acquisition device20 includes a display 40 that displays the signals from the receivingprocessor as well as status signals generated by ECG data acquisitiondevice 20 itself The display can be implemented as a series of LEDlights with one light indicating the appropriate location for the fourthelectrode in the current measurement.

It should be noted that splitting the ECG recording between the ECG dataacquisition device and the receiving processor makes a small ECG dataacquisition device possible, since the ECG data acquisition device doesnot need to include the additional electronics for processing thesignals to ECG recordings and for transmitting that information to athird party when necessary. In addition to reducing the electronics, thefunctional split also reduces the size of the battery needed to powerthe ECG data acquisition device, which, in tum, also makes a smaller ECGdata acquisition device possible. As noted above, limiting the size ofthe ECG data acquisition device is critical to ensuring that the devicewill be with the patient when the patient perceives that the patient maybe having a cardiac event. In one embodiment, the receiving processorprovides the display functions of display 40 discussed above. However,embodiments in which the various functions are split in a differentmanner between the ECG data acquisition device and the receivingprocessor can also be constructed.

In practice, the user signals the receiving device or the receivingprocessor that the user is ready to make set of ECG recordings. Thissignal can be generated by a button on the ECG data acquisition deviceor by the act of moving the ECG data acquisition device from storageconfiguration to the extended configuration. If the display on thereceiving processor is used for this function, the user signals thereceiving processor, which sends the appropriate signals to the ECG dataacquisition device.

The receiving device then initializes the relevant application on thereceiving device and sends a command that activates one of the LEDs. Theuser then touches the corresponding three electrodes with the user'sfingers and places the fourth against the user's body at the indicatedlocation. When ECG data acquisition device 20 detects that all of theelectrodes are in contact with the user, ECG data acquisition device 20begins transmitting the relevant signals to the receiving processor. Thesignals can be sent as analog signals or digitized by an analog todigital converter with ECG data acquisition device 20 and sent asdigital signals. When the receiving processor has received sufficientdata for the signal in question, the receiving processor signals theuser by activating another LED or causing the ECG data acquisitiondevice to make an audible signal using an acoustical signal generator42. The receiving processor then activates another LED that signals theuser to move to the next position for the fourth electrode.

The division of the computational labor between the ECG data acquisitiondevice and the receiving device can be adjusted to reflect the amount ofelectronics that can be conveniently placed in the ECG data acquisitiondevice and the desired battery life of the ECG data acquisition deviceon a single charge of its batteries. In embodiments that have greatercomputational capacities, the ECG data acquisition device can performmost, if not all, of the computational activities. In such embodiments,the receiving device is used as a relay to a remote site that mayinclude medical personnel, and, optionally, as a more extensive displayscreen than can be conveniently placed on the ECG data acquisitiondevice without the space constraints of the ECG data acquisition devicein the storage configuration.

It should be noted that the preferred mode of communication between theECG data acquisition device and the receiving processor can depend onother functions provided by the ECG data acquisition device. As notedabove, embodiments in which the ECG data acquisition device serves someadditional function such as an electronic key are advantageous inassuring that the ECG data acquisition device is carried by the user.The frequencies utilized in providing these other functions aretypically set by the functions in question. For example, the frequencieswith which an electric key for use in a keyless ignition system in anautomobile operate are set by the car manufacturer and are notnecessarily one of the frequencies used in wireless communications forcomputer systems. Hence, an ECG data acquisition device that is toprovide this additional frequency must provide a communication link thatoperates at that the dual use frequency. The ECG data acquisition devicealso needs to communicate with the receiving processor, which may use adifferent frequency or frequencies for its wireless communications.

In one aspect of the present invention that operates with such dual useECG data acquisition devices, the receiving processor is modified to usethe dual use frequency rather than providing two separate frequencies inthe ECG data acquisition device. This reduces the power consumption andcomplexity of the ECG data acquisition device. It is typically easier toequip the receiving processor with a separate communication channel thatis used to communicate with the ECG data acquisition device than to adda second frequency to the ECG data acquisition device, since, thereceiving processor typically has fewer power constraints than the ECGdata acquisition device.

Refer again to FIG. 6 . It should be noted that the receiving processorcould be a processor that provides a network interface to anotherprocessor or processors. For example, the ECG data acquisition devicecould communicate with the processor in a vehicle that is connected tosatellite service 65 that provides emergency and other services. Thesatellite server is typically linked to a computer network. To simplifythe drawings, the links between the satellite server and the computernetwork have been omitted. Such services automatically call foremergency vehicles when the air bags are deployed in a car. The GPSreceiver in the car provides the location of the car having the problem.In this case, the ECG data acquisition device could communicate on theexisting Blue Tooth link in the car that is used for connecting tocellular telephones, and other electronic devices. A patient in the carwho has concerns can then perform an ECG and communicate the results tothe automobile computer. The automobile computer could process theresults and inform the patient of the results or just communicate theresults to a central processor at the satellite service. The satelliteservice could provide processing and/or a relay service to send theresults to an appropriate medical site.

Utilizing the automobile's ability to act as the receiving processor isparticularly advantageous in that the automobile can communicate bysatellite even in areas that lack cellular telephone service. Inaddition, the patient could be receiving an ECG in route to a hospitalso that the results are forwarded to the hospital ahead of the patient'sarrival.

The above-described embodiments utilize wireless communications forcoupling the ECG data acquisition device to the receiving processor.This wireless link can also be used for downloading updated software oruser specific information such as a reference ECG. In one aspect of theinvention, a multi-purpose connector is also supplied for connecting theECG data acquisition device to a receiving processor for transmittingcontrol signals or other communications to the ECG data acquisitiondevice and for charging the batteries in the ECG data acquisition deviceby connecting the ECG data acquisition device to a suitable chargingdevice. Refer again to FIG. 3A. A connector 77 is optionally included inthe ECG data acquisition device. Connector 77 is configured to accept aplug that has a set of ten conventional ECG electrodes for recording aconventional 12 trace ECG that is administered by a third party on thepatient. In addition, connector 77 also accepts a cable having aconventional computer communication link such as a USB communicationlink. Connector 77 utilizes this conventional communication link tocharge the batteries in ECG data acquisition device 20 as well asdownload information such as software updates and/or patient specificinformation. While connector 77 is shown at a specific location on ECGdata acquisition device 20, connector 77 can be located at other points.

In one aspect of the invention, a controller 78 in the ECG dataacquisition device recognizes the different possible mating connectorsthat are inserted into connector 77 and alters its functionsaccordingly. For example, if controller 78 detects the presence of theconventional ECG electrodes discussed above, the controller disregardsthe signals from electrodes 21-24 and performs a conventional 12 leadECG recording that is communicated to the receiving processor. Ifcontroller 78 detects a conventional communication bus connected toconnector 77, the controller can receive commands from the device at theother end of the communication bus and perform the indicated functionssuch as updating the software in the ECG data acquisition device.

In one aspect of the invention, ECG data acquisition device 20 includesa compartment 43 that is sized to hold a medication to be taken by thepatient if the receiving processor or, a medical facility incommunication with the receiving processor, determines that thepatient's ECG recordings differ significantly from a referencerecordings stored in the receiving device for that patient. For example,if the current ECG recordings differ significantly from the referencerecordings the receiving processor could send the recordings to amedical facility that normally treats the patient or contact anemergency unit. If the staff of that facility determines that thepatient is at risk for a cardiac event, the patient would be instructedto take the medication in compartment 43 by activating a predeterminedindicator on the ECG data acquisition device or the receiving processorand then proceed to the nearest medical facility that can treat thepatient or send an ambulance to the patient's location as determined bya position locating system included in ECG data acquisition device 20 orthe receiving processor with which ECG data acquisition device 20communicates. Early treatment with simple medications has been shown toincrease positive outcomes for patients with cardiac events. Themedication may be a vascular dilator such as nitroglycerin, or othermedication prescribed by the patient's regular physician. In one aspectof the invention, the medication is aspirin. In one aspect of theinvention, the compartment is only opened in response to a signal fromthe receiving processor. If the receiving processor determines thatthere is a significant change in the patient's ECG recordings and cannotcontact the appropriate facility, the receiving processor may beprogrammed to open the compartment and instruct the patient to go to anemergency ward or similar facility for a checkup. Alternatively,compartment 43 can be opened manually, and the receiving processorprovides instructions to the user to open the compartment and take themedication.

The above-described embodiments require that the ECG data acquisitiondevice measure the signals from the left and right hands by measuringthe signals from electrodes 22 and 23 described above. Providing areproducible pressure and contact area between the finger and theelectrodes has been found to significantly improve the measured signals.In one aspect of the invention, the electrodes include ridges or otherstructures that engage the bone of the user's finger if the user pusheson the electrode with a force greater than some predetermined force.

Refer now to FIGS. 8A and 8B, which illustrates one embodiment of afinger electrode that can be utilized with the present invention. FIG.8A is a top view of electrode 100, FIG. 8B is cross-sectional view ofelectrode 100 through line 8B-8B. Electrode 100 includes an electricallyconducting region 101 that is connected to the electronics that measurethe signals from the user's finger. An insulating finger support such asinsulating ridge 102 supports the user's finger 103 such that the pad104 of the finger makes contact with contact area 101. If the userincreases the pressure on insulating ridge 102 in an attempt to increasethe pressure between pad 104 and electrically conducting region 101, theridge engages the bone in the user's finger and prevents the finger frommoving further toward electrically conducting region 101. As a result,the pressure between the pad and the electrode as well as the area ofcontact is approximately constant after the applied force of the fingeron the electrode structure exceeds some predetermined force.Accordingly, as long as the user presses the user's finger on theelectrode with a sufficient force, a reproducible contact area and forceis achieved.

It should be noted that insulating ridge 102 can be constructed from aring of material that is glued onto electrically conducting region 101.The dimensions of the ring can be adjusted for the particular patientfor whom the ECG data acquisition device is being provided. Thecustomizable dimensions include the horizontal spacing of the ridge andthe height of the ridge. Increasing the height of the ridge increasesthe minimum pressure with which the patient must press on the electrodestructure. The spacing of the ridge is determined by the size of thepatient's finger.

While the finger support shown in FIGS. 8A and 8B utilizes an insulatingridge that is attached to the conducting area that is part of theelectrode structure, other arrangements for controlling the contact areaand contact pressure between the patient's finger and the electrode thatmeasures the ECG signals could be utilized. The important feature of thefinger support is that it reduces the variation in the contact area andcontact pressure between the patient's finger and the electrode as afunction of the force with which the patient presses on the electrodestructure.

As noted above, common mode noise is a significant problem in ECGrecordings. One method for further reducing this noise in the standardleads is to always form the difference of two signals at differentpoints on the patient body. In the prior art, the standard leads arecomputed by measuring the signals discussed above with reference to Eqs.(1). In one aspect of the present invention, it has been foundexperimentally that reduced noise equivalent traces to those shown inEqs. (1) can be obtained by first measuring the difference between thesignals on each of the limbs in question relative to Wilson CentralTerminal and then computing leads I, II, and III from thesemeasurements. In the conventional standard lead measurements, lead II ismeasured as the difference between the potential on an electrodeconnected to the left leg and an electrode connected to the right hand,and Lead 1 is measured as the difference between the potential on anelectrode connected to the left hand and an electrode connected to theright hand.

In this aspect of the invention, the signals from electrodes 22-24 arecombined to provide the Wilson Central Terminal signal and thedifference between the potential on this combined terminal and each ofelectrodes 22-24 is then measured. The lead I, II, and III signals arethen constructed from these measured signals. Denote the sum of thepotentials on electrodes 22-24 by

V _(w)=(V ₂₂ +V ₂₃ +V ₂₄)/3

Where V₂₂, V₂₃, and V₂₄ are the potentials on electrodes 22-24. Denotethe measured difference between V_(w) and V₂₃ by V_(LH), The measureddifference between V_(w) and V₂₂ by V_(RH), and the measured differencebetween V_(w) and V₂₄ by V_(LG). In general, these measured differenceswill also depend on a gain factor A. Hence, at channels outputs:

V _(LG) =A*(V ₂₄ −V _(w))

V _(RH) =A*(V ₂₂ −V _(w))

V _(LH) =A*(V ₂₃ −V _(w))

By definition, at channels outputs:

Lead I=A*(V ₂₃ −V ₂₂)=V _(LH) −V _(RH)

Lead II=A*(V ₂₄ −V ₂₂)=V _(LG) −V _(RH)

Lead III=A*(V ₂₄ −V ₂₃)=V _(LG) −V _(LH)

Hence, the conventional standard lead traces can be obtained from themeasurements that are made relative to the Wilson Central Terminal. Asnoted above, it has been found experimentally that this arrangementyields standard lead traces that have lower noise.

The above-described embodiments of the present invention have beenprovided to illustrate various aspects of the invention. However, it isto be understood that different aspects of the present invention thatare shown in different specific embodiments can be combined to provideother embodiments of the present invention. In addition, variousmodifications to the present invention will become apparent from theforegoing description and accompanying drawings. Accordingly, thepresent invention is to be limited solely by the scope of the followingclaims.

It is the intent of the Applicant(s) that all publications, patents andpatent applications referred to in this specification are to beincorporated in their entirety by reference into the specification, asif each individual publication, patent or patent application wasspecifically and individually noted when referenced that it is to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention. To the extent that section headings are used,they should not be construed as necessarily limiting. In addition, anypriority document(s) of this application is/are hereby incorporatedherein by reference in its/their entirety.

What is claimed is:
 1. A system for recording a plurality of ECG traces,said system comprising: an portable ECG acquisition device having aplurality of outer surfaces and sized to be held by a user between firstand second fingers of a first hand of the user when in use, a first ofsaid plurality of outer surfaces having a first ECG electrode configuredto be contacted by the first finger of the first hand of the user, asecond of said plurality of outer surfaces having a second ECG electrodeconfigured to be contacted by a finger of a second hand of the user, anda third of said plurality of outer surfaces having a third ECG electrodeconfigured to be contacted by a body portion of the user, said first,second, and third ECG electrodes configured to be simultaneouslycontacted by the first finger of the first hand, the finger of thesecond hand, and the body portion of the user; wherein said ECGacquisition device includes a controller configured to at least one of:a. collect a set of data from said first, second, and third ECGelectrodes when said first and second, and third ECG electrodes aresimultaneously in electrical contact with the first finger of the firsthand of the user, the finger of the second hand of the user, and one ofa plurality of different locations on the user's body portion,respectively; and b. collect sequential data sets when said third ECGelectrode sequentially electrically contacts each of the plurality ofdifferent locations on the user's body portion while said first andsecond ECG electrodes are simultaneously in electrical contact with thefirst finger of the first hand of the user and the finger of the secondhand of the user, respectively; and a receiving processor configured: c.to receive from said ECG acquisition device at least one of said dataset, if collected according to (a), and to generate a set of standardlead traces; d. to receive from said ECG acquisition device thesequential data sets, if collected according to (b), and to generate thesix precordial traces (V₁-V₆); wherein the receiving processor isconfigured to: analyze the at least one ECG recording generated; anddetermine whether or not the user is at risk of a cardiac event.
 2. Thesystem of claim 1, wherein said controller is configured to measuresequential signals from said ECG electrodes as a function of time, whilethe first and second ECG electrodes make electrical contact with thefirst finger of the first hand and the finger of the second hand,respectively, and the third ECG electrode sequentially makes electricalcontact with each of the plurality of locations on the user's body. 3.The system of claim 1, wherein said device includes a fourth ECGelectrode configured to contact one of: a location on the first hand ofthe user other than a location of contact of the first ECG electrodewith the first finger of the first hand of the user; and a location onthe second hand of the user other than a location of contact of thesecond ECG electrode with the finger of the second hand of the user;wherein said ECG acquisition device includes a circuit configured togenerate a common mode cancellation signal injected through said fourthECG electrode.
 4. The system of claim 1, wherein said wherein said ECGacquisition device includes a circuit configured to generate a commonmode cancellation signal injected through one of said first, second, andthird ECG electrodes.
 5. The system of claim 1, further including adisplay configured to display an appropriate electrode location to theuser via said ECG acquisition device.
 6. The system of claim 1, whereinthe body portion is selected from the lower abdomen of the user and oneof the user's legs.
 7. The system of claim 1, wherein third electrode isconfigured to be contacted by a precordial measurement point on theuser.
 8. The system of claim 7, wherein said precordial measurementpoint depends on the ECG recording being generated.
 9. The system ofclaim 1, wherein said receiving processor is configured to collect theset of data according to (a) and said circuitry is configured togenerate an ECG recording including said set of standard lead traceshaving lower noise than that of the common mode signal of the user'sbody.
 10. The system of claim 1, wherein said device is foldable from afirst configuration, wherein said second and third ECG electrodes faceopposite directions, to a second configuration, wherein said second andthird ECG electrodes face a same direction.
 11. The system of claim 1,wherein said device includes a first surface having a circularcross-sectional profile, said first ECG electrode having a curvedsurface extending at least partly around said first surface.
 12. Thesystem of claim 1 wherein, in (d), said receiving processor isconfigured to combine said sequential data sets collected from thefirst, second, and third ECG electrodes; wherein said sequential datasets are used to determine the six precordial traces (V₁-V₆).
 13. Thesystem of claim 1 wherein, in (d), precordial leads are computed ascombinations of potentials at the first and second hands and precordialpositions at the chest.
 14. The system of claim 1 wherein, in (c), saidreceiving processor is configured to construct lead I, II, and IIIsignals from the measured differences, where a sum of the potential on said ECG electrodes is denoted by:V _(w)=(V ₂₂ +V ₂₃ +V ₂₄)/3, wherein V22, V23, and V24 are thepotentials on said first, second, and third ECG electrodes.
 15. Thesystem of claim 12, wherein said receiving processor is configured tocalculate: a measured difference between Vw and V23 by VLH; a measureddifference between Vw and V22 by VRH; and a measured difference betweenVw and V24 by VLG; wherein said measured differences are dependent on again factor A.
 16. The system of claim 15, wherein, at channels outputs:VLG=A*(V24−Vw)VRH=A*(V22−Vw)VLH=A*(V23−Vw) wherein, at channels outputs:Lead I=A*(V23−V22)=VLH−VRHLead II=A*(V24−V22)=VLG−VRHLead III=A*(V24−V23)=VLG−VLH.
 17. The system according to claim 1,wherein the third ECG electrode is configured to be sequentially incontact with the user's left leg or lower abdomen and with each of aplurality of different locations on the user's chest while the first andsecond ECG electrodes are in contact with the first finger of the user'sfirst hand and the finger of the user's second hand, respectively, saidcontroller configured to collect the sequential data sets when saidthird ECG electrode electrically sequentially contacts: a. the user'sleft leg or lower abdomen; and b. the plurality of different locationson the user's chest while said first and second ECG electrodes aresimultaneously in electrical contact with the first finger of the user'sfirst hand and the finger of the user's second hand, respectively; andwherein said receiving processor is configured to receive the sequentialdata sets from said ECG acquisition device, and is configured togenerate an ECG recording consisting of standard lead traces andprecordial traces from the sequential data sets received.
 18. The systemof claim 1, wherein said system includes a display configured toindicate a location on the body portion of the user at which the thirdECG electrode should contact the body portion simultaneously when thefirst and second ECG electrodes are in contact with the first finger ofthe user's first hand and the finger of the user's second hand,respectively.
 19. The system according to claim 18, wherein said displayis located on said receiving processor and wherein said receivingprocessor is selected from: a smart phone, a personal data assistant(PDA), a tablet computer, a laptop personal computer, and a non-portablecomputer.
 20. The system according to claim 1, wherein said receivingprocessor is configured to determine a probability of a cardiac event.21. The system according to claim 1 wherein said receiving process isconfigured to generate an alert if the user is at risk of a cardiacevent, when the risk is exceeds a predetermined threshold; and whereinsaid receiving processor is configured to at least one: instruct theuser to take a medication; transmit the ECG recording to a medicalfacility or to an emergency unit; and transmit instructions for the userto proceed to a medical facility for treatment; if the user is at riskof a cardiac event.
 22. A method of recording a plurality of ECG tracesusing an ECG acquisition device and a receiving processor, said methodincluding: a) holding the device with between first and second fingersof a first hand, wherein the first finger of the first hand contacts afirst ECG electrode on a first outer surface of the device; b)contacting a second ECG electrode on a second outer surface of thedevice with a finger of a second hand of a user; c) contacting a thirdECG electrode on a third outer surface of the device with one of aplurality of different locations on a body portion of the user; whereinsaid (c) is performed sequentially for each of the plurality ofdifferent locations on the body portion of the user while simultaneouslyperforming both said (a) and (b) sequentially collecting by said ECGacquisition device sequential sets of information from said first,second, and third ECG electrodes; generating by said receiving processoran ECG recording from the sets of information collected from said first,second, and third ECG electrodes; and analyzing the ECG recording by thereceiving processor, determining the probability of a cardiac event, andgenerating an alert when a predefined threshold is exceeded.
 23. Amethod of using an ECG acquisition device and a receiving processor todetermine a probability of a cardiac event of a user, said methodincluding: a) holding the device with between first and second fingersof a first hand of the user, wherein the first finger of the first handcontacts a first ECG electrode on a first outer surface of the device;b) contacting a second ECG electrode on a second outer surface of thedevice with a finger of a second hand of the user; c) contacting a thirdECG electrode on a third outer surface of the device with one of aplurality of different locations on a body portion of the user; whereinsaid (c) is performed sequentially for each of the plurality ofdifferent locations on the body portion of the user while simultaneouslyperforming both said (a) and (b) sequentially collecting by said ECGacquisition device sequential sets of information from said first,second, and third ECG electrodes; generating by said receiving processoran ECG recording from the sets of information collected from said first,second, and third ECG electrodes; analyzing by said receiving processorthe ECG recording, determining the probability of a cardiac event, andgenerating an alert when a predefined threshold is exceeded; andgenerating an alert by said receiving processor.